Inspired by the intermittent locomotion of fish schools, numerical simulations are performed with two self-propelled flexible fins in a side-by-side configuration with anti-phase oscillation actuated by laterally constrained heaving motions. For an intermittent swimming gait, one type of the half-tail-beating mode (HT mode) and two types of multiple-tail-beating modes coasting at the smallest (MTS mode) and largest (MTL mode) lateral gap distances are applied. Similar to the continuous-tail-beating mode (CT mode), equilibrium lateral gap distances between two fins with HT and MTL modes exist, whereas two fins with MTS mode do not maintain a lateral equilibrium state. Although the cycle-averaged lateral force acting on two fins with CT and MTL modes is mostly determined by an outward deflected jet and enhanced positive pressure between two fins, an added-mass lateral force related to an asymmetric flapping kinematics by passive flexibility also plays an important role in MTL mode to achieve a stable state with a lateral gap distance smaller than that in CT mode. When the cruising speed or the cycle-averaged input power is identical in a stable state, the cost of transport (COT) for two fins with MTL mode is smaller than that with CT mode due to not only a benefit from the intermittent swimming gait but also an enhanced schooling benefit with a small equilibrium lateral gap distance. The COT for two fins with CT mode is reduced further when the bending rigidity increases, whereas it is opposite with MTL mode.

Identification of geographical areas with high burden of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission in schools using spatial analyses has become an important tool to guide targeted interventions in educational setting. In this study, we aimed to explore the spatial distribution and determinants of coronavirus disease 2019 (COVID-19) among students aged 3–18 years in South Korea. We analysed the nationwide epidemiological data on laboratory-confirmed COVID-19 cases in schools and in the communities between January 2020 and October 2021 in South Korea. To explore the spatial distribution, the global Moran's I and Getis-Ord's G using incidence rates among the districts of aged 3–18 years and 30–59 years. Spatial regression analysis was performed to find sociodemographic predictors of the COVID-19 attack rate in schools and in the communities. The global spatial correlation estimated by Moran's I was 0.647 for the community population and 0.350 for the student population, suggesting that the students were spatially less correlated than the community-level outbreak of SARS-CoV-2. In schools, attack rate of adults aged 30–59 years in the community was associated with increased risk of transmission (P < 0.0001). Number of students per class (in kindergartens, primary schools, middle schools and high schools) did not show significant association with the school transmission of SARS-CoV-2. In South Korea, COVID-19 in students had spatial variations across the country. Statistically significant high hotspots of SARS-CoV-2 transmission among students were found in the capital area, with dense population level and high COVID-19 burden among adults aged 30–59 years. Our finding suggests that controlling community-level burden of COVID-19 can help in preventing SARS-CoV-2 infection in school-aged children.

The explosive outbreak of COVID-19 led to a shortage of medical resources, including isolation rooms in hospitals, healthcare workers (HCWs) and personal protective equipment. Here, we constructed a new model, non-contact community treatment centres to monitor and quarantine asymptomatic and mildly symptomatic COVID-19 patients who recorded their own vital signs using a smartphone application. This new model in Korea is useful to overcome shortages of medical resources and to minimise the risk of infection transmission to HCWs.

It has been reported that the follower in a tandem configuration with no wall (0W) reduces the time-averaged input power by utilizing the vortex interception mode (Zhu et al., Phys. Rev. Lett., vol. 113, 2014, p. 238105). In the present study, a numerical simulation is conducted with two self-propelled flexible fins in the tandem configuration near a single wall (1W) and two parallel walls (2W). Contrary to the vortex interception for 0W, the follower employs spontaneously a mixed mode (i.e. a combination of the vortex interception mode and the slalom mode) for 1W and the slalom mode for 2W. Although the lateral motion of the follower for 0W, 1W and 2W is synchronized with the induced lateral flow generated by the leader, the time-averaged input power of the follower for 1W and 2W is reduced significantly due to the enhanced lateral flow by the vortex–vortex interaction near the wall. The jet-like flow opposite to the moving direction continuously hinders the movement of the follower for 0W, whereas the follower for 1W and 2W utilizes the negative horizontal flow when passing between the main vortex and the induced vortex near the wall, leading to a decrease of the thrust force acting on the follower allowing the follower to keep pace with the leader. The global efficiency of the schooling fins is optimized with a small heaving amplitude of the follower and a critical value of phase difference between the leader and follower when the values of the wall proximity and bending rigidity are moderate.

Background: Recently, healthcare-associated infections (HAIs) in long-term care hospitals (LTCHs) have markedly increased, but no infection control policy has been established in South Korea. We investigated the current HAI surveillance system and executed a point-prevalence pilot study in LTCHs. Methods: HAIs were defined by newly established surveillance manual based on McGeer criteria revised in 2012. Three LTCHs in Seoul and Gyeonggi province were voluntarily recruited, and data were collected from up to 50 patients who were hospitalized on August 1. The medical records from September to November 2018 were retrospectively reviewed by a charge nurse for infection control per each hospitals after 1 day of training specific for LTCH surveillance. All data were reviewed by a senior researcher visiting onsite. Results: The participating hospitals had 272.33 ± 111.01 beds. Only 1 hospital had an onsite microbiological laboratory. In total, 156 patients were enrolled and 5 HAIs were detected, for a prevalence rate of 3.2%. The average patient age was 79.04 ± 9.92 years. The HAIs included 2 urinary tract infections, skin and soft-tissue infection, low respiratory infection, and conjunctivitis. Conclusions: This is the first survey of HAI in LTCHs in South Korea. The 3.2% prevalence rate is lower than those from previous reports from the European Union or the United States. This study supports the development of a national HAI surveillance and infection control system in LTCHs, although implementation may be limited due to the lack of laboratory support and infection control infrastructure in Korea.

Funding: None

Disclosures: None

For decades, fructose intake has been recognised as an environmental risk for metabolic syndromes and diseases. Here we comprehensively examined the effects of fructose intake on mice liver transcriptomes. Fructose-supplemented water (34 %; w/v) was fed to both male and female C57BL/6N mice at their free will for 6 weeks, followed by hepatic transcriptomics analysis. Based on our criteria, differentially expressed genes (DEG) were selected and subjected to further computational analyses to predict key pathways and upstream regulator(s). Subsequently, predicted genes and pathways from the transcriptomics dataset were validated via quantitative RT-PCR analyses. As a result, we identified eighty-nine down-regulated and eighty-eight up-regulated mRNA in fructose-fed mice livers. These DEG were subjected to bioinformatics analysis tools in which DEG were mainly enriched in xenobiotic metabolic processes; further, in the Ingenuity Pathway Analysis software, it was suggested that the aryl hydrocarbon receptor (AhR) is an upstream regulator governing overall changes, while fructose suppresses the AhR signalling pathway. In our quantitative RT-PCR validation, we confirmed that fructose suppressed AhR signalling through modulating expressions of transcription factor (AhR nuclear translocator; Arnt) and upstream regulators (Ncor2, and Rb1). Altogether, we demonstrated that ad libitum fructose intake suppresses the canonical AhR signalling pathway in C57BL/6N mice liver. Based on our current observations, further studies are warranted, especially with regard to the effects of co-exposure to fructose on (1) other types of carcinogens and (2) inflammation-inducing agents (or even diets such as a high-fat diet), to find implications of fructose-induced AhR suppression.

Raman scattered O VI features at 6825 Å and 7082 Å found in symbiotic stars are important spectroscopic tools to probe the mass transfer process. Adopting a Monte Carlo approach, we perform a profile analysis of Raman O VI features of the yellow SySt AG Draconis and make a comparison with the spectrum obtained with CFHT. It is assumed that the accretion flow is convergent on the entering side with enhanced O VI emission and the flux ratio F(1032)/F(1038)∼1, whereas on the opposite side the flow is divergent with low O VI emission and F(1032/F(1038)∼2. Our best fit to the spectrum is obtained from our model with a mass-loss rate of the giant ∼4 × 10−7 M⊙ yr−1. A slight red wing excess in the spectrum suggests the presence of bipolar neutral components receding in the directions perpendicular to the binary orbital plane with a speed ∼70km s−1

We trace Sn nanoparticles (NPs) produced from SnO2 nanotubes (NTs) during lithiation initialized by high energy e-beam irradiation. The growth dynamics of Sn NPs is visualized in liquid electrolytes by graphene liquid cell transmission electron microscopy. The observation reveals that Sn NPs grow on the surface of SnO2 NTs via coalescence and the final shape of agglomerated NPs is governed by surface energy of the Sn NPs and the interfacial energy between Sn NPs and SnO2 NTs. Our result will likely benefit more rational material design of the ideal interface for facile ion insertion.

Allicin (AL) regulates the cellular redox, proliferation, viability, and cell cycle of different cells against extracellular-derived stress. This study investigated the effects of allicin treatment on porcine oocyte maturation and developmental competence. Porcine oocytes were cultured in medium supplemented with 0 (control), 0.01, 0.1, 1, 10 or 100 μM AL, respectively, during in vitro maturation (IVM). The rate of polar body emission was higher in the 0.1 AL-treated group (74.5% ± 2.3%) than in the control (68.0% ± 2.6%) (P < 0.1). After parthenogenetic activation, the rates of cleavage and blastocyst formation were significantly higher in the 0.1 AL-treated group than in the control (P < 0.05). The reactive oxygen species level at metaphase II did not significantly differ among all groups. In matured oocytes, the expression of both BAK and CASP3, and BIRC5 was significantly lower and higher, respectively, in the 0.1 AL-treated group than in the control. Similarly, the expression of BMP15 and CCNB1, and the activity of phospho-p44/42 mitogen-activated protein kinase (MAPK), significantly increased. These results indicate that supplementation of oocyte maturation medium with allicin during IVM improves the maturation of oocytes and the subsequent developmental competence of porcine oocytes.